1. Subject Matter of the Invention
The subject of the invention are novel, very economic processes for the preparation of:
nitrated aryl polymers and optionally aminated aryl polymers prepared therefrom by a reduction of the nitro group;
aryl polymers containing both nitro groups and sulfonic acid groups or both amino groups and sulfonic acid groups.
The subject of the invention are also novel, modified aryl polymers which can be produced very economically and aryl polymer membranes produced therefrom:
a nitrated aryl polymer and an aminated aryl polymer which can be produced therefrom;
a nitrated and sulfonated aryl polymer;
an aminated and sulfonated aryl polymer;
membranes made from the novel aryl polymers and blends of the polymers of the invention with additional polymers.
In addition, the subject of the invention is the application of the newly developed aryl polymers in membrane processes, in particular as polymeric electrolytes in electromembrane processes, e.g., in electrodialysis and in the PEM membrane fuel cell. Since the inventive membranes have high chemical and thermal stabilities, they are an economical alternative to the very expensive perfluorinated ionomeric membranes of the Nafion type which have mainly been used in PEM fuel cells up to the present.
2. The State of the Art
[Ref. 1] describes the preparation of nitrated poly(etheretherketone) (PEEK-NO2) by dissolving the PEEK in methanesulfonic acid and subsequently nitrating by adding concentrated nitric acid. A drawback of this process is the use of the relatively expensive methanesulfonic acid as the solvent.
[Ref. 2] describes the preparation of amino-terminated poly(etheretherketone) oligomers by the nucleophilic displacement reaction of 4,4xe2x80x2-difluorobenzophenone by hydroquinone in the presence of a calculated excess of m-aminophenol. A drawback of said oligomers is a low amino group content, since only the terminal groups are modified by amino groups. There exist various patents for the preparation of sulfonated poly(etheretherketone) by dissolving the PEEK in concentrated sulfuric acid, with [Ref. 3] being one example thereof. In [Ref. 3], however, only sulfonated poly(etheretherketones) are disclosed.
Naik et al. [Ref. 4] describe the preparation and the properties of backbone-aminated poly(ether sulfone) (PES) and poly(etherether sulfone) (PEES), where the aminated polymer has been prepared by the nitration of the base polymer using nitrating acid (HNO3/ H2SO4) in nitrobenzene as the solvent and the subsequent reduction of the nitro group to the amino group. A drawback of this process is the toxicity of the nitrobenzene solvent.
There are numerous works regarding the nitration of aryl polymers, of which the works of Crivello [Ref. 5] and Daly [Ref. 6] may be mentioned here. The authors use ammonium nitrate and trifluoroacetic anhydride as nitrating agents. The drawback of this method is the high cost of trifluoroacetic anhydride and the liability to explosion of ammonium nitrate.
The present invention provides sulfonated and nitrated polymers having an aryl backbone comprising a plurality of aryl groups R1, R2, or both, connected by bridging groups selected from the group consisting of R5, R6, R7 and R8; wherein: 
R3, and R4 H, methyl, or 4-phenoxybenzoyl, and
x=1 or 2,
said polymer having at least a portion of the aryl groups of the backbone substituted with xe2x80x94SO3H and at least a portion of the aryl groups of the backbone substituted with xe2x80x94NO2.
The invention also provides for processes for producing the sulfonated and nitrated polymers.
The invention further provides aminated and sulfonated polymers prepared by reduction of the nitrated and sulfonated polymers, containing primary amino groups in place of the nitro groups on the aryl backbone. In addition, the invention further provides aminated and sulfonated polymers having secondary or tertiary amines or quaternary ammonium groups prepared by alkylation of the primary amines on the aminated and sulfonated polymers.
The polymers of the invention can be combined with additional polymers to form polymer blends.
A still further aspect of the invention provides for membranes comprising the polymers and polymer blends and a process for producing the membranes from the polymers of the invention and polymer blends.
A further object of the invention is the use of such membranes in electromembrane processes, e.g., in electrodialysis and in membrane fuel cells composed of the membranes of the invention.